Gel electrophoresis is a standard tool in biochemistry and molecular biology to separate molecular components, such as DNA, RNA or protein, either for subsequent identification or in a preparative procedure. In gel electrophoresis, the different mobility of ions under the influence of an electric field (a function of electrical charge and/or density) serves to separate molecular fragments as they move linearly in the porous medium. It is common to then transfer the separated fragments to a membrane that binds the fragments permitting further processing directed toward making an image ("blot") visible so that identification can be accomplished.
Ordinarily this transfer is done with the separated bands distributed along the body of the gel, the driving force having been removed when adequate separation has occurred. A membrane is placed on top of the gel so that the bands transfer laterally to the membrane. This is known as a Southern Blot and many variations are available.
An alternate procedure, direct blot, is described by Pohl in U.S. Pat. Nos. 4,631,120 and 4,631,122. There the bands are run to the end of the gel and transferred to a moving belt that is in contact with the end of the gel.
In U.S. Pat. No. 5,234,559 incorporated by reference herein there is disclosed an improved direct blot process and apparatus in which the bands are transferred from the end of the gel to a moving membrane that is held on a frame. The framed membrane is then subjected to the further manual or automatic processing steps required to make an image visible for identification such as the steps described in U.S. Pat. Nos. 4,717,653 and 5,087,558 by Webster, Jr. which can be followed by analysis such as that described by Hubner in U.S. Pat. No. 4,885,697. The frame is a considerable aid to the physical handling and transport of the membrane which by itself is highly flexible and incapable of self support.
Frames, and their general use in analysis and electrophoresis, are known in the art.
Hurd et al., in U.S. Pat. No. 4,812,216, 4,818,360, and U.S. Pat. No. 4,913,791, teaches a framed membrane to facilitate blotting and transfer of the membrane to and from a plurality of processing stations.
Dahms in U.S. Pat. No. 4,111,784 and 4,207,166, teaches bonding a support membrane to a bowed frame "to keep it stretched and wrinkle-free".
Dwyer et al. in U.S. Pat. No. 3,759,773, laminates a plastic base sheet to a microporous plastic membrane (the electrophoretic medium). The combination is bowed.
These and other references relating to frames are deficient in not providing means to maintain the membrane flat and taut in use and particularly so when used at a temperature that relaxes the plastic structure. The instant invention overcomes this deficiency.